Air conditioning system



p 3 1941- G. H. GILDERSLEEVE ETAL 2,257,462

AIR CONDITIONING SYSTEM 7 2 Sheets-Sheet 1 Filed April 25, 1938Jnvmtorsr W H.

(Ittorneg p 1941- G. H GILDERSLEEVE ET AL 2,257,462

AIR CONDITIONING SYSTEM Filed April 25, 1958 2 Sheets-Sheet 2 attorneyPatented Sept. 30, 1941 AIR CONDITIONING SYSTEM IGondon H. Gildersleeve,Cranford, NY. J., and Ernest Graber, Douglaston, N. Y., assignors toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn., acorporation of Delaware Application April 25, 1938, Serial No. 204,084

16 Claims.

This invention relates to an air conditioning system and moreparticularly to a system for providing automatic year around controlofthe temperature and humidity of thespace to be conditioned.

for the return air around the heating and cooling means is alsoprovided, this by-passalso being controlled by suitable dampers. A freshair temperature responsive device controls the fresh and return airdampers to position the fresh air dampers in open position and thereturn air dampers in closed position whenever the outdoor temperatureis ata predetermined value, as for example, 70. Whenever the outdoortemperature rises above or falls below this value, the fresh air dampersare moved towards closed position and the return air dampers are movedtowards open position. A device responsive to the temperature of thereturn air controls the positions of the return air dampers and thebypass dampers whenever the fresh air dampers are closed to close thereturn air damper and open the by-pass damper whenever the return airtemperature falls below a predetermined value. A heating coil is locatedin the bypass so that when the return air passes through this by-pass,if the return air temperature or the dischai'ge temperature are belowcertain values the air entering the air conditioning chamber through theby-pass is heated. The heating means in the air conditioning chamber iscontrolled by a device responsive to the dew-point temperature of theair leaving the cooling means which is in the form of a spray so that asthis dew-point temperature falls below a predetermined value, the airpassing through is heated by the heating coil. The tempenature of thespray is also controlled by a. device responsive to the dew-pointtemperature of the air leaving the spray so that as this dew-pointtemperature rises above a certain value the temperature of the spray isreduced accordingly. A set of minimum fresh air dampers are provided forpermitting some fresh air to be admitted to the air conditioning chamberat all times when the system is in operation, and a preheat coil isprovided for heating the fresh air passing through.

the minimum fresh air dampers, this coil being ture falls below apredetermined value such as 35, for example, heat will be supplied tothis coil. A device responsive to the humidity of the outdoortemperature also controls the fresh air dampers to close the samewhenever the outside humidity rises above a predetermined valueregardless of the outdoor temperature.

It is accordingly an object of our invention to provide an improved allyear around air conditioning system.

More specifically it is an object of our invention to provide an airconditioning system of the type wherein fresh and return air is suppliedto an air conditioning chamber to be conditioned, the fresh and returnair supplied being suitably controlled so that a maximum amount of freshair is admitted to the chamber whenever the outdoor temperature is at adesired value, wherein the return air is supplied to the chamber bymeans of a by-pass around suitable air conditioning means within thechamber whenever the fresh air being supplied to the chamber is at amaximum value, wherein the amount of return air which is by-passedaround the heating and cooling elements in the air conditioning chamberis controlled by a return air temperature responsive device whenever theamount of fresh air entering a chamber is less than the maximum underthe control of a device responsive to the outside temperature so thatwhen this temperavalue, and wherein the by-pass is provided with asuitable heating element controlled in accordance with the return airtemperature and the discharge air temperature.

A further object of the invention is the provision of a novel controlmeans for a set of dampers whose position'is selectively controlled bytwo different. conditions or controlled conjointlyby the two conditions,depending upon the values of the conditions.

Another object of the invention is the provision of three sets ofdampers, one pair of said sets of dampers being simultaneously operatedby one condition responsive means, and another pair of said sets ofdampers being simultaneously operated by a second condition responsivemeans.

Another object of the invention is the provision of an air conditioningchamber having fresh and return air inlets, spray means within thechamber, a by-pass for leading return air around the spray means, meansfor circulating water for the spray means through a cooling chamber,condition responsive means for controlling the flow of air through thefresh and return air inlets and the by-pass, means for by-passing spraywater around the cooling Referring more particularly to Figure 1, an

air conditioning chamber is represented generally by the referencecharacter III., This chamber includes a fresh air inlet ll a return airduct l2, and a discharge duct 13. A return air inlet l5 for theadmission of air entering the chamber I 6 through the return air duct I2is provided. A by-pass l6 connects the return air duct l2 with anotherinlet l1 positioned downstream from the-return air inlet i5. A fan 26driven by a suitable motor 2| is provided for drawing air through thechamber l6 and discharging it through the duct l3- which leads to asuitablespace or spaces to be conditioned.

Two sets of dampers are positioned in the chamber H! for controlling theadmission of fresh air thereto. The first set of dampers 22 may betermed minimum fresh air dampers since they are always open duringoperation of the system thus permitting the supply of a minimum amountof fresh air at all times as will be more clearly set forth hereinafter.The fresh air dampers 23 are positioned in a manner to be laterexplained in accordance with the temperature of the outdoor and also inaccordance with thehumidity of the outdoor air. The return air inlet iscontrolled by suitable dampers 24,'

there being a by-pass 25' around these dampers for admitting a minimumsupp y of return air through the inlet 15 to the chamber l6 at alltimes. -Dampers 25 positioned in the inlet l1 control the fiow of airthrough the by-pass l6 to be explained. 4

Power is supplied to the fan motor 2| through suitable conductors 26,21, and 26 controlled by a suitable switching means 29 which connectsthe conductors 26, 21, and 26 to a suitable source of power, not shown.It will be understood that when the switch 29 is in the positionillustrated power is supplied to the motor 2| and the fan 26 is operatedto draw air through the chamber 16 and discharge the same through thedischarge passageway l3. Connected to the conductors 21 and 26 by meansof conductors 36 and 3| is a coil 32 of a relay generally designated bythe reference character 33. This relay also includes an armature 34, aswitch arm 35, and contacts 36 and 31 cooperating with this switch arm.When the relay coil 32 is energized, the arm 35 is moved into engagementwith the contact 36, and upon deenergization of this coil the arm 35 ingconnected between terminals 43 and 44 and the other field winding beingconnected between terminals 44 and 45. Power may be supplied to themotor by means of conductors 46 and 41 connected to any suitable sourceof power, not shown. When terminals 43 and 44 are connected together oneof the field windings is energized to cause the motor to operate toposition the dampers 22 in open position as illustrated. Theenergization of the other field winding by connecting terminals 44 and45 together causes the motor to rotate to move the dampers 22 to closedposition. It will readily be seen that when the relay 33 is energized,terminals 43 and 44 are connected together through conductors 56,contact 36, arm 35, and conductor 51, and upon deenergization of therelay 33, the arm 35 moves. into engagement with contact 31 andterminals 44 and 45 are connected together by means of conductors 5| arm35,.contact 31, and conductor 52. In this manner, whenever switch 29 isclosed to cause operation of the fan 26, relay 33 isenergized causingdampers 22 to move to open position.

Mounted just ahead of the dampers 22 is a heating coil which may besupplied with any suitable heating medium and controlled by a suitablevalve 56. The position of valve 56 is controlled by a motor 56 which maybe similar in construction tothe motor 46, this motor being providedwith an arm 59 connected by means of a link 66 to a valve stem 6|. Theoperation of motor 56 is controlled by a mercury switch 62 havingterminals 63, 64, 65, and 66 and a mercury element 61. Terminal 63 isconnectedby means of a conductor 66 to the terminal 69 of the motor 56,terminal 16 of the motor is connected by means of the conductor 1| tothe switch termi nals 64 and 65 and terminal 12 of the motor isconnected by means of conductor 13 to the switch terminal 66. Whenterminals 16 and 12 of the motor are connected together the motoroperates to move the valve 56 to closed position and upon connecting theterminals 69 and 16 to- 41 gather, the motor operates to open the valve56. to the air conditioning chamber II in a manner moves by gravity orby means of any suitable Switch 62 is mounted upon a lever 15 pivoted at16 and biased by means ofa spring 11 against a pin 16 connected to thetop of a bellows 19. The bellows 19 is connected by means of a capillarytube 66 to a bulb 6| mounted in the fresh air inlet II, the tube, bulb,and bellows'being filled with a suitable volatile fluid. When thetemperature of the air passing over the bulb 6|-drops to a low enoughvalue as for example 35", the volatile fluid contained within the bulbcontracts thus permitting the bellows 19 to contract and the spring 11to move the switch 62 to the other position in which the terminals 63and 64 are connected by meansof the mercury element 61 whereupon themotor 56 operates to open the valve 56 and supply steam or othersuitable heating medium to the coil 55.

The dampers 23 are connected by means of a link 62 to a crank disc 63which is rotated by means of the motor 64. This motor may be of the typeillustrated in Patent 2,028,110 issued to D. G. Taylor on January 14;1936, and the construction thereof is shown in detail in Figure 2. Thismotor may consist of a pair of armatures 65 and 66 which are selectivelyenergized by means of field windings 66 and 61, respectively, and causerotation of the armature shaft 69 in one direction or the otherdepending upon which of the field windings is energized. The armatureshaft 69 may be connected by means'of suitable reduction gearing 98 to agear 9| mounted on a shaft 92 carrying the crank disc 83. The selectiveenergization of field windings 8'! and 88 is controlled by means of arelay 95, this relay including opposed balanced windings 96 and 91, anarmature 98, and an arm 99 cooperating with contacts I88 and IN. Whenwindings 96 and 91 are equally energized, the armature 98 moves to themid-position as illustrated wherein arm 99 is in engagement with neithercontact I88 nor MI. The energization of winding'96 to a greater extentthan the winding 9I causes the arm 99 to move into engagement withcontact IN and the energization of winding 91 to a greater extent thanwinding 96 causes the arm 99 to move into engagement with contact I88.The junction of the field windings 81 and 88 is connected to a line wireI82 and the arm 99 is connected by means of a conductor I83 to line wireI84. Line wires I82'and I84 may be connected to a suitable source ofpower, not shown.

When the arm 99 is in engagement with contact IN the winding 81 isenergized by means of the following circuit: from the line I84 toconductor I83, arm 99, contact I8I, conductor I86 through the winding 81and to the line I82. The armature 86 is accordingly energized aridrotates in a direction to cause the'fresh air dampers to move towardsclosed position. When thearm 99 is in engagement with the contact I88the field winding 88 is energized by the following circuit: from theline I84 through conductor I83, arm 99, contact; I88, conductor I85,winding 88 back to the line I82. Armature 85 is now rotated to causerotation of shaft 92 and crank disc 83 carried therebyto rotate in thedirection to move the dampers 23 towards open position. Connected tothel ines 882 and I84 is the primary I88 01 a step-down transformer I89.The secondary II8 of this transformer is connected by means offconductors III and H2 to the opposite ends of the windings 96 and 91 ofthe relay 95. The junction of these coils is connected by means ofconductors, H5 and M6 to the terminals II! and H8 of a mercury switch I28. The terminal I2I of this switch is connected by means of a con-'-ductor I22 to an arm I23 of the bell crank "lever I24 which'is pivotedat I25; the upper portion of this arm being suitably insulated from therest.

of a conductor I32 to the end of relay coil 96 through a protectiveresistance element I33.

The opposite ends of the resistance I 3| are con-.

nected together by means of conductors I35 and I36 and are connected tothe end of relay coil 91 by means of conductor I31 and protectiveresistance I38. It will be noted that when the switch I28 and the armI23 of potentiometer I38 are in the positions illustrated, that therelay coil 91 is more highly energized than the relay coil 96- since theonly resistance in series with the coil 91 is the resistance I33 andaccordingly arm 99 moves into engagement with the contact I88 and fieldwinding 88 is energized to cause rotation'of shaft 92 in a direction tomove the fresh air dampers 23 towards open position. Also mounted on theshaft 92 rotated by the armature shaft 89 is an arm I 48 suitablyinsulated therefrom and cooperating with a resistance I,4I, this arm andresistance forming a balancing potentiometer for the motor 84. The leftend of re- I42 and resistance I33 to.the left end of relay coil 96 andthe opposite end of resistance I is' connected by means of conductor I43and reout and the coils 96 and 91 are equally energized and the arm 99is therefore in mid positionbetween the contacts I88 and IN. Movement ofarm I23 to either the right or the left from the 7' positionillustrated.when the arm I48 is in the position illustrated, will cause the coil 96of rela to become more highly energized than the coil 91 whereupon thearm 99 will be moved into engagement with contact I8 and field coil 81will cause rotation of armature 86 and shaft 92 in a direction to movethe fresh air dampers towards closed position. The armature. 86 willcontinue to rotate until the arm I48 has moved suiiiciently far towardthe left or resistance I to balance the eifect of the movement of thearm I23 over resistance I3I. In this manner the motor rotates in adirection to close' the fresh air dampers whenever the arm I23 deviatesfrom the center position, an amount proportional to the amount of thedeviation of the arm I23.

The bell crank lever I24 which includes the arm I23'also includes an armI58 biased by means of a spring I5I into engagement with a pin'.orplunger I52 extending upwardly from the top of a bellows I53. Thisbellowsis connected by means of a capillary tube I54 to a bulb I55mounted in the fresh air inlet II, the tube, bulb, and bellows-beingfilled with a suitable volatile fluid which expands or contracts inresponse to temperature changes. This bulb and bellows is so arrangedthat when the fresh air temperature is at a predetermined value as forexample 70, the arm I23 will be in the mid position illustrated withrespect to the resistance I3I. As the outdoor temperature falls, thefluid within the bulb I 55 contracts and the arm I23 moves tosuch thatthe fresh air dampers 23 are wide open. As the fresh air temperatureincreases or decreases the motor rotates in a direction. to

move the dampers 23 towards closed position, v

the extent of movement of the dampers being proportional to the changein the outdoor temperature above or below 78. It will be obvious thatwhen the arm' I23 reaches either end of re-' sistance I3I, that the armI48 of the balancing potentiometer will have to move to the extreme leftend of resistance MI in order tobalance the effect of the controlpotentiometer I38 and when the arm I48 is in thisposition the motor willhave rotated sufficiently to move the dampers 23 to their fully closedposition. The range of temperatures through which the arm I23 moves maybe chosen as desired and may be for example the extreme left end ofresistance I3I, at 75 the arm will have'moved to the. extreme right endof the resistance and the arin I23 will be in the 65 to 75. Thus at 65,the arm in will be at when the arm m is in the l mid position with theoutdoor temperature at 70.

1. The mercury switch I20 is carried by a lever I55 pivoted at I56 andbiased in a counter-clockwise direction by means of a spring I51.Connected to the right of the pivot I56 is a suitable humidityresponsive element. I 58 mounted within the fresh air inlet II/theopposite end of this element being suitably fixed as at I60. Thishumidity responsive element may be formed of any suitable material thatexpands in accordance with a rise in humidity and. contracts upon adecrease in humidity. If the element I58 expands sufficiently due to arise in humidity of the .air entering the air conditioning chamber, thearm I55 will pivot to such a position under the influence of the biasingmeans I51 that the contacts H1 and H9 of the switch I20 are connectedtogether by the mercury element. When this happens the coil 96 will bemore highly energized than the coil 91 since the only resistance inseries and armature 86 will rotate and cause the dampers 23 to movetowards closed position. This rotation of the motor will continue untilthe dampers are fully closed since the effect of switch I20 will not bebalanced until the arm I40 has moved to the extreme left end ofresistance I4I. It will thus be seen that when the humidity of the airentering the chamber I is at a sufficiently high value, thefresh airdampers 23 will be completely closed regardless of the temperature ofthe air entering the 'chamber.

The position of the dampers 24 is controlled by a motor I60. An arm I6Idriven by this motor is connect-ed by means of a link I62'to thedampers. struction to motor 84 and includes a pair of armatures I 65andoI66'operated by means of field windings I61 and I68, respectively.armatures are mounted on a shaft I69 connected by means of a reductiongearing I10 to a shaft I1I carrying the arm' I6I. A relay I12 similar tothe relay 95 of the motor 84 is provided. This relay includes opposedbalanced coils I13 and I14 connected together at one end and connectedby means of conductors I15 and I16 to secondary I11 of a step-downtransformer I18. The primary, l19 of this transformer is connected toline wires I80 and I 8| which are connected to a suitable source ofpower, not shown. Relay I12 also includes an armature 84 influenced bythe coils I13 and I14 and'connected to an arm I85 cooperating with fixedcontacts I86 and I81.

When the coil I 13 is more highly energized than the coil I14, the arm I85 is moved into engagement with contact I86 and the field winding I61of the motor I 60 is energized through the following circuit: from theline I80 through conductor I90, arm I85, contact I86, conductor I8I,winding I61, and conductor I92 to the line wire I8I. The motor I60 isnow rotated in a direction to move the return air dampers towards openposition. When the winding I14 becomes more highly energized than thewinding I13 the armature I84 is moved to the right and moves the arm I85into engagement with the contact I81. Field winding I68 is now energizedby means of the following circuit: from the line wire I80 to conductorI90, arm I85, contact I81, conductor I94, winding I68, and conductor I92to the line wire I8I. The energization of winding I68 causes Thismotormay be similar in con-.

The

the motor to rotate in a direction to move the dampers towards openposition. When fleld windings I13 and I14 are equally energized orbalanced against one another, the armature I84 moves to the mid positionillustrated in which arm I85 engages neither contact I86 nor I81,neither field winding is energized and the motor is at rest. 7

Connected to the junction of the coils I13 and I14 by means of aconductor 200 is an arm 20I connected to and insulated from the shaft 92driven by the motor 84. The arm 20I is arranged to move across'aresistance 202 when the motor 84 is in operation. The lower end ofresistance 202 is connected by means of conductors 203, 204, andaprotective resistance 205 to the left end of the coil I13. The oppositeend of the resistance 202 is connected by means of conductors 201, 208,a resistance 209, conductors 2I0, 2| I, and a protective resistance 2I2to the right end of thecoil I14. When the arm 20I is at the lowerextremity of resistance 202 it will be apparent that the coil I14 ismore highly energized than the coil I13 and the armature I66 isaccordingly energized to cause the motor to rotate in 'a direction tomove the dampers 24 towards closed position.

Carried by the shaft Ill and insulated therefrom is the arm 2I0 of abalancing potentiometer resistance 2I5. This arm is moved by the motorI60 in an opposite sense from the arm 20I of the motor 84 whereby theeifect of the arm 20I is balanced by the arm 2I0. The arm 2 I0-isconnected by means of conductors 2| 3 and 200 to the junction of thecoils I12 and I 13. The right end of the resistance 2I5 is connected bymeans of conductors 2I6 and resistance 205 to the left end of the coil I13. The opposite end of the resistance 2 I5 is connected by means of aconductor 220 and resistance 2| 2 to the right end of the coil I14. Whenthe arm 20I is at the lower extremity of resistance 202 as illustratedthe motor I60 will rotate until the arm 2I0 is at the left end ofresistance 2I5, as illustrated, whereby the effect of potentiometerresistance 202 is counter-acted and the relay coils I13 and I14 areequally energized, the armature I84 is in the mid position and the motorI60 is at rest. It'

will therefore be apparent that as long as the fresh air dampers are intheir wide open position and arm 20I is in the position illustrated, thereturn air dampers 24 will be in their fully closed position so that theonly air entering the chamber I0 through the return air inlet I5 will bethrough the small by-pass 25'. As the fresh air dampers begin to movetowards closed position in response to the outside air temperaturerising above or falling below 70 the arm 20I is moved by the shaft 92upwardly over the resistance 202 an amount proportional to the extent ofmovement of the dampers 23. As the arm 20I moves upwardly over theresistance 202 the coil I13 becomes more highly energized than the coilI14 and the arm I85 moves into engagement with the contact I86 whereuponthe armature I65 of the'motor I60 is driven to move the return airdampers towards open position. At the same time the arm 2I0 of thebalancing potentiometer is moved towards the right of the resistance 2I5and the motor I60 will continue to rotate until the effect of thepotentiometer 202 on the relay I12 is balanced by the movement of thearm 2I0 over the resistance 2I5. Accordingly it will be seen thatdampers 24 will move an amount proportional to the movement of dampers23 in an opposite direction. 'In other words as dampers 23 move towardsclosed position, the dampers 24 are movedtowards open position.

A second potentiometer 226 also exercises a control over the motor I60at certain times. This potentiometer includes a resistance 226 and anarm 221 arranged to sweep thereover, this arm being pivoted at 228 andforming part of a lever including arm 229. The arm 228 is biaseddownwardly by means of a spring 230 into engagement with a pin orplunger 23I extending upwardly from a bellows 232. Bellows 232 isconnected by means of a capillary tube 233 to a bulb 234 mounted in thereturn air duct I 2. The tube, bulb, and bellows may be filled with asuitable volatile fluid which expands or contracts in accordance withchanges in the return air temperature. As the return air temperatureincreases the .bellows 232 expands and the arm 221 is moved downwardlyover the resistance 226. The arrangement may be such that arm 221 is atthe upper extremity of resistance 226 when the return air temperature isbelow 73 F. and upon a rise in return air temperature to 75 the arm 221may be moved to the lower extremity of the resistance 226. The upperportion of resistance 226 may be connected by means of conductors 235and 204 and resistance 205 to the left end of relay coil I13. Theopposite end of resistance 226 may be connected by means of conductor231, conductor 2H, and resistance 2I2 to the right end of relay coilI14. The arm 221 of the potenti ometer 225 is connected by means ofconductors 240 and 201 to the upper end of resistance 202. When the arm20I is in the lower position illustrated the relay coil I13 will beshorted out except for the resistance 205 and the potentiometer 225 willhave no effect on the relay I12. Therefore regardless of the return airtemperature, the return air dampers will always be in their fully closedposition whenever the fresh air dampers are in their wide open position.However as thefresh air .dampersstart to move towards closed position byreason of the outdoor temperature rising above or falling below 70 andthe arm 2| moves upwardly over the resistance 202 both.

the potentiometers 202 and 225 will act to control the motor I60, andthe position of the return air dampers. When the fresh air damperstremity of resistance 202 and it is intended at this time that thecontrol of the return air damper should be by the potentiometer 225. Inorder that potentiometer arm 20I exercises no control over the dampermotor I60 when in its upper extreme position, the resistance 208 whichis of the same resistance value as resistance 202 is positioned betweenthe upper end of the resistance 202 and the right end of relay coil I14so that the effect of the resistance 282 is nullified. It will be notedthat when the arm 221 is at the upper extremity of resistance 226 andthe arm 2" is at the upper extremity of resistance 202 then coil I14 ismore highly energized than coil I13 whereupon arm I85 is moved intoengagement with contact I81 and the motor rotates in a direction toclose the return air dampers 24. If the return air temperature risesabove the lower limit of potentiometer 225, or in other words; risesabove 73", the arm 221 begins to move downward- 1y over resistance 226and the resistance in series with coil I13 begins to decrease whereasthe resistancein series with soil H4 increases. Arm I05 now moves intoengagement with contact I86 thus energizing the field winding I61whereupon shaft I1I rotates in a direction toopen the return air dampersan amount proportional to the rise in the return air temperature. Afterthe effect of potentiometer 225 has been balanced by the balancingpotentiometer 2I5 the motor will come to rest. It will be understood ofcourse, that if the fresh air dampers are only partly closed and arm 2Mis intermediate the ends of resistance 202 that the position of themotor I60 will be controlled by the combined effects of potentiometers202 and 225.

It will now be understood that whenever the fresh air damper is wideopen, the'return air damper will be fully closed regardless of thereturn air temperature, also when the fresh air dampers are closed andthe return air temperature is above 75 the return air dampers will befully opened, but whenever the fresh air dampers are fully closed andthe return air temperature is below 75 the return air dampers will bemoved towards closed position dependingupon how far below 15 the returnair temperature is. In other words, when the outdoor temperature is at70 the fresh air dampers are opened and the return air dampers areclosed but whenever the fresh air temperature rises above or drops below70 the fresh air dampers start to closeand the return air dampers startto open assuming the return air temperature is sufiiciently high, but ifthe return air temperature is below the 75 limit the return air dampersare moved in accordance with the return air temperature and the freshair temperature.

The position of the by-pass dampers 25 is controlled by a motor 250which may be similar in construction to the motors 84 and I60. Since theconstruction of these motors has been clearly set forth, illustration ofthe internal wiring of this motor is not deemed necessary. Arm 25I isoperated by this motor and is connected by means of link 252 to thedampers 25. Motor 250 is controlled by potentiometer 255 which includesa resistance 256 and arm 251. This arm is rigid with the arms 221 and229 and rotates therewith as is apparent in the drawing. A conductor 260connects the arm 251 with the junction of the relay coils of thebalancing relay within the motor. Conductor 26I connects the left endsof resistance 256 with the extremity of one of these relay coils andconductor 262 connects the right end of resistance 256 with theextremity of the other relay coil. Conductors 264 and 265 which may beconnected to a suitable source of power are provided for supplying powerto the motor.

When the arm 251 of potentiometer 255 is in the extreme right positionillustrated the motor 250 is operated to position the dampers 25 intheir maximum open position. The arm 251 will be in this positionwhenever the return air temperature is below 73. Upon a rise in returnair temperature the arm 251 moves towards the left and the motor 250 isoperated to move the dampers 25 towards closed position. When the returnair-temperature reaches 75", the arm 251 is moved to its extreme leftposition and the dampers 25 are moved to their fully closed position. Inthis position it .will be understood that the arm 221 is at the lowerextremity of the resistance 226 and the return air dampers 24 arepositioned in accordance with the position of the fresh air dampers 23as heretofore explained. It will now be seen that the fresh and returnair dampers 23 and 24 are. positioned in accordance with the fresh airtemperature and the return air dampers 24 are also controlled by thereturn 1 air temperature as are the by-pass dampers 25.

For the purpose of cooling and washing the air, a spray 210 ispositioned in the chamber l and is supplied with water from a tank 21l.A pump 212' is provided for supplying water to the spray This valve maybe automatically controlled in accordance with the temperature of thewater in the chamber and for this purpose is provided with a suitableoperating bellows or diaphragm mechanism 280 connected by means of acapillary tube 28| to a bulb 282 positioned within the tank 2". The tubeand bulb may be filled with a suitable volatile fluid which exerts aforce on the mechanism 280 in accordance with the temperature of thewater within the tank 21! so that as the temperature of the water in.the tank increases the valve is automatically opened to admit morecooling fluid to the coil 218 whereby a predetermined temperature may bemaintained within the tank. Any suitable means, (not shown), may beprovided for maintaining a fixed supply of water in the tank 21 I.

A suitable by-pass 285 connects the pipe 215 and the pipe 213 above thetank 21!, the flow.

through this by-pass being controlled by means of a suitable three-wayvalve 286." When this valve is in one extreme position all the watercirculated by the pump 212 must flow through the cooling tank 21l andwhen the valve is in the other extreme position, all the watercirculated by the pump is by-passed around the tank 21l. As thevalveimoves between its extreme positions varying proportions of waterare circulated through the tank and by-passed around the tank so thatthe temperature or the water issuing from the spray 210 is effectivelycontrolled.

A motor 290 which may be similar in construction with the motors 84 andI60 is provided for controlling the position of the valve 286, an arm291 being rotated by the motor and being conpletely by=passed positionand the tank 21! effects no cooling of the water being supplied in thechamber Hi. When the dampers 2-3 are moved to their closed position, thecam 298 is rotated by the shaft 92 to a position wherein the switch 295is tilted to its opposite position and terminals 306 and 301 areconnected together by the mercury element within the switch. The motor298 is now controlled by a controller genfilled with a suitable volatilefluid whereupon the arm 3 I2 is positioned in accordance with thetemperatureof the fluid within the bulb 3".

This bulb is positioned immediately downstream of the spray 210 so thatit responds to the dewpoint temperature of the air leaving the spray.

When the switch 295 is tilted in the opposite direction in response to aclosure of the fresh air dampers 23, the junction of the relay coilswithin the motor 290 is connected by means of conductors 308, terminals306 and 301 of the switch 295 and conductor 320 to the arm 3l2 ofpotentiometer 3. The terminal 30I of the motor 290 is connected by meansof conductors 302 and 32l to the left end of the resistance 31 I. Theterminal 322 which connects to the extremity of the other relay coilwithinthe motor 290 from that which is connected to terminal 30l isconnected by means of conductor 324 to the right end of resistance 3. Itwill accordingly be seen that when the mercury switch 295 is tilted inthe position opposite to that illustrated that the motor 290 will becontrolled solely by the controller 3|0. If the dew-point temperature ofthe air leaving the spray 210 rises above a predetermined value, as forexample the valve 286 will be operated by the motor 290 to by-pass lessof the water around the tank 211 293. It is desired when the fresh airdam rs 23 are in wide open position, indicating that the.

outdoor air is at the proper temperature and cooling thereof isunnecessary, that the valve 286 be in the extreme position wherein allthe water circulated by the pump 212 is by-passed around the tank 2".For this purpose a mercury switch 295 is carried by a lever 296 pivotedat 291 and positioned by means of a cam 298 operated by the shaft 92which is rotated by the motor 84. Whenever the fresh air dampers areopen, the lever 296 rests upon a low portion of the cam 298 and theswitch 295 is in the position illustrated. In this position the relaycoil connected between terminals 300 and 30! (Figure 2) is shorted outby the mercury switch 295 as follows: from the terminal 301 throughconductors 302, 303, terminal 304 of the switch 295 through the mercuryelement to the terminal 305 and conductor 308 to the terminal 300. Withthese and circulate more of the water through the tank thus maintaininga minimum dew-point temperature of the air leaving the spray 01 55.

Mounted upstream from the spray 210 is a heating coil 338 through whichany suitable heating medium such as steam may be circulated. A valve 33lcontrols the flow of heating medium through the coil 338 and a motor 332similar to the motors 84 and may be provided for controlling theposition of this valve. An arm 333 is operated by the motor 332 and isconnected by means of a link 334 to valve stem 335. A controller 340 isprovided for controlling the operation of motor 332. This controller maycomprise a potentiometer resistance 34! with which cooperates an arm 342forming one arm of a bell crank lever pivoted at 343, the other am 344of the lever cooperating with the pin 345 of the bellows 346. A spring341 biases the lever 344 against the pin 345. Bellows 346 is connectedby means of a capillary tube 350 with a bulb I 351 "mounted justdownstream from the spray 210. This bellows, tube, and bulb may befilled with a suitable volatile fluid and since the bulb 35| is mountedjust downstream from the spray 210 the controller 340 will respond tothe dewpoint temperature or the air leaving the spray 210.

A conductor 355 connects the arm 342 with the junction of the relaycoils within the motor 332,

the opposite ends of these coils being connected by means of conductors356 and 351 with the opposite ends of the resistance 34!. When thedewpoint temperature of the air leaving v spray 210 is above apredetermined value such 45,

the arm 342 will be positioned at the right end 10 of resistance 34!, asillustrated, and the motor will position the valve 33! in fully closedposition. If the dew-point temperature of the air leaving the spray 210drops below 45,fthe arm 342 begins to move towards the left whereuponthe motor 332 begins to open the valve 33!, thus per-' mitting thesupply of a heating medium to the coil 330 in accordance withthedew-point temperature for maintaining this temperature at 45. It'will beunderstood of course that whenever the valve 33! is open to admit theheating medium to the coil 330, the dew-point temperature of the airleaving the spray will be so low that the valve 286 will be in thecompletely bypassed position so that the water issuing from motors 84and I60 is providd for controlling the position of the valve 366. Anarm366 is'operated by the motor 361 and is connected by means of a-link 369with a valve stem 310. The motor 361 is controlled in accordance withthe return air temperature and also the discharge air temperature. Acontrol 315 responsive to the return air temperature includes an arm 316pivoted at 311 and arranged to move over a potentiometer resistance 318.Arm 380 rigid with arm 316 is biased by means of spring 36 intoengagement with pin or plunger 382 connected to bellows 383. Thisbellows is connected by means of a capillary tube 334 to a bulb 385mounted in the return air duct !2, the tube, bulb, and bellows beingfilled with a suitable volatile fluid so that arm 316 is positioned inaccordance with the return air temperature. Controller 390 responds tothe discharge air temperature and includes arm 39f cooperating withresistance 392,

the arm being pivoted at 393 and having an arm 394 rigid therewith andbiased by spring 395 into engagement with pin or plunger 396 connectedto bellows 391. This bellows is connected by means of a capillary tube398 to a bulb 399 positioned in the discharge duct !3. The tube, bulb, 5

and bellows are filled with a suitable volatile fluid and it will bereadily apparent that arm 39! will be positioned in accordance with thedischarge air temperature. The controller 390 is intended to function asa low limit controller to cause the opening of valve 366 whenever theair being discharged through the duct !3 falls below. a predeterminedvalue such as It will therefore be seen that normally the arm 39! willbe positioned at the extreme right end of the resistance 65 392 exceptwhen the discharge air temperature falls below this predetermined value.The main control over the motor 361 is by the controller 315 whichresponds to the return air temperature. This may be so arranged as tocontrol the motor between the temperatures of 70 and 72. Thus wheneverthe return air temperature is above 72 the arm 316 will be at the rightend of resistance 318. If the return air temperature falls below thisvalue the arm 316 will begin to 75 series with the other relay coil.

move towards the left and whenever the return I air temperature drops to70, for example, the

arm 316 will be positioned at the opposite end of resistance 310.

The junction of the relay coils of motor 361 is connected by means ofconductor 400 to the arm 39!. The terminal 40! of the motor connects tothe extremity of one of the relay coils and. this terminal is connectedby means of conductors 405 and 406 to the left end of resistance 392 andby means of conductors 405 and 401 to the left end of resistance 318.The terminal 402 of the motor is connected to the extremity of the otherrelay coiland this terminal isconnected by means of conductors 4!!! and4!! to the right end of the resistance 318. Arm 316 of the controller315 isconnected by means of conductor 2 to the right end of resistance392. When the controllers 315 and 390 are in the positions illustrated,relay coil connected to terminal 402 of the motor is shorted out throughthe following circuit: through conductor 400, arm 39!, conductor 2,,arm'316, and conductors 4!! and M0 to the terminal 402. With this relaycoil shorted out the motor, 361Qoperates to completely close the valve366 so that no heat is supplied to the coil 365. If the temperature ofthe return air now drops. below 72 the arm 316 begins to move towardsthe left and increase the resistance in shunt with the coil connected tothe terminal 402 at the same time decreasing resistance in I The motor361 now operates to open the valve an amount proportional to themovement of arm 316 over the resistance 318 and it will be seen thatwhen arm 316 is at the opposite extremity of resistance 318 the motorwill operate to completely open the valve 366 wherebyrrnaximum heat isbeing suppliedto the air by the coil 365. The temperature at which thistakes place may be at 70 for example. It is intended that during thistime the resistance 392 of controller 390 should have no efiect on themotor 361 since'the discharge air temperature is above 65. Theresistance 392 is connected between the center motor terminal and theterminal 40! through the arm 39!. Accordingly a second resistance 420having a resistance' value equal to that of resistance 392 is connectedby means of the arm 39! between the center motor terminal and theterminal 402 whereby the effect of resistance 392 is balanced out by theresistance 420 when the arm 39! is in, the extreme right position.

Assuming now that the return air temperature is at 72, or higher, thearm 316 will be-in the position shown calling for closing of the valve366. If now the discharge air temperature should fall below 65, the arm39! will move towards the left over resistance 392 thus addingresistance in the circuit in shunt'with the coil between the centerterminal and terminal 402 whereupon the motor moves the valve towardsopen position an amount depending upon the movement of arm 39! to theleft. It will therefore be seen that the valve is controlled primarilyin accordance with return air temperatures but in case the discharge airtemperature falls below a desired value, the valve is opened regardlessof the return air temperature. This condition is more likely to existduring the cooling season and it is undesirable that air be supplied tothe space below a certain temperature as 21765 to prevent the existenceof a cold draft within the space being conditioned.

It is believed that the'operation of the system will now be apparent butit may be briefly summarized as follows: the fresh air dampers 23 willbe open whenever the outside temperature is at a desired value providingthat the humidity of the outside air is not excessive. As the outsideair temperature increases or decreases above or below thisidesired valuewhich may be chosen as 70", the fresh air dampers move towards closedposition and above 75 or below 65 the fresh air I dampers will beentirely closed. Regardless of the outside air temperature, whenever thehumidity of the outside air reaches an excessive value the fresh airdampers will also be closed.

The minimum fresh air dampers are however open at all times duringoperation of the system and the air passing through these dampers ispreheated whenever the outdoor temperature falls below a certain valuesuch as 35.

The dampers 24 in the return air inlet are closed whenever the fresh airdampers are wide open. Whenever the fresh air dampers start to movetowards closed position the return air dampers 24 begin to move towardopen position if the return air temperature is suficiently high. Ifhowever,,the return air temperature falls below a desired value such as75, the return air dampers 24 will tend to move towardsclosed po-' withfresh air temperature, the return air dampers are operated in accordancewith fresh and return air temperatures, and the by-pass dampers arecontrolled in accordance with return air temperature. I

The-temperature of the cooling and washing spray 210 is controlled inaccordance with the position of the fresh air dampers and inaccordancewith the dewpoint temperature of the air passing through thespray. As long as the fresh air dampers 23- are open', the watercirculated through the spray 210 is not cooled whatever, but wheneverthe fresh air dampers are completely closed the temperature of the sprayis controlled in accordance with the dewpoint temperature of the airpassing therethrough so that this dewpoint temperature is kept below amaximum value of 55, for example. The heating coil 33!! is alsocontrolled in accordance with the dewpoint temperature of the airleaving the spray to maintain a minimum dewpoint temperature of 45, forexample. Thus, whenever this dewpoint temperature drops below 45, heatis supplied to the air passing through the spray by means of the coil330 but should the dewpoint temperature rise above 55 the heating call330 will of course be inoperative and the water circulated by the spraywill be cooled in accordance with the dewpoint temperature to keep itdown to 55.

The heating coil 365 is controlled primarily by .the return airtemperature so that should this .turn air is down to 72 the return airdampers 24 will be closed and the-by-pass dampers 25 will be open sothat heat is supplied to the air by means of the coil 365. The coil 365will also provide heat whenever the discharge temperature is below 65regardless of the return air temperature, thus preventing the existenceof a cold draft within the space being conditioned.

It will now be seen that I have devised .a very complete airconditioning system whereby automatic year around control is providedand where by the system is operated most economically at all times.Thus, when the outdoor temperature is at a desired value and no heatingor cooling thereof is necessary the fresh air dampers are open thusadmitting a maximum amount of fresh air and the temperature of the washwater will be substantially the same as the fresh air so that no coolingthereof is necessary.

It should be understood that the various temperature values referred tothroughout the specification are illustrative only, and that anysuitable temperature values maybe chosen in actual N practice. I-I-Iaving described the preferred form of our invention, manymodifications will become apparent to those skilled in the art and wewish it to'be understood that this invention is'limited-only by thescope of the appended claims.

We claim as our invention:

1. In an air conditioning system, an air conditioning chamber having afresh air inlet, a return air inlet, conditioning means within saidchamber for changing the-heat content of air flowing therethrough, meansfor conducting air from a space being conditioned to said return airinlet, a by-pass for conducting air from said conducting means aroundsaid conditioning a means to said conditioning chamber, means forcirculating air through said air conditioning chamberand a space to beconditioned, damper means in control ofsaid fresh air inlet, said returnair inlet and said by-pa'ss, means influenced by a first conditionvarying with the heat conptent of the fresh air in control of the dampermeans controlling said fresh air inlet and said return air inlet, meansinfluenced by the heat content of the return air also in control of thedamper means controlling said return air inlet and the damper means incontrol of said bypass, and -means influenced by a second conditionvarying with the heat content of-the fresh air also in control of thedamper means controlling the fresh air inletyand the return air inlet.

In an air conditioning system, an air conditioningfchamber having afresh air inlet, a return air inlet, conditioning means within saidchamber for changing the heat content. of the fresh air, means forconducting air from a space being conditioned to said return air inlet,a bypass for conducting air from said conducting means around saidconditioning means to said conditioning chamber, means for circulatingair through, said air conditioning chamber and a space to beconditioned, dampermeans in control effect of the conditioning means,and means influenced by a second condition varying with the heat contentof the fresh air also in control of the damper means controlling thefresh air inlet and the return air inlet.

3. In an air conditioning system, anair conditioning chamber having afresh air inlet, a'return air inlet, cooling means within said chamber,means for conducting air from a space being conditioned to said returnair inlet, a by-pass for conducting air from said conducting meansaround said cooling means to said conditioning chamber, means forcirculating air through said air conditioning chamber and a space to beconditioned,dampermeansincontrol of said fresh airinlet,saidreturnairinletand said by-pass, means responsive to thetemperature of the fresh air for controlling the damper means in controlof the fresh air inlet and the return air inlet to provide for admissionof a maximum amount of fresh air and a minimum amount of return air whenthe temperature of the fresh air is at a predetermined value and tograduatingly decrease the amount of fresh air and to increase the amountof return air as the temperature of the fresh air rises above or fallsbelow said predetermined value, and means responsive to the temperatureof the return air also in control of the damper means controlling saidreturn air inlet and the damper means controlling said by-pass toincrease the amount of air admitted through said return air inlet and todecrease the amount of air by-passed' around said cooling means as thetemperature of the return air increases above a predetermined value.

4. In an air conditioning system, an air conditioning chamber having afresh air inlet, a return air inlet, cooling means within said chamber,means for conducting air from a space being conditioned to said returnair inlet, a by-pass for conducting air from said conducting meansaround said cooling means to said conditioning ditioning chamber, meansfor circulating air through said air conditioning chamber and a space tobe conditioned, damper means in control of said fresh air inlet, saidreturn air inlet and said by-pass, means responsive to the condition ofthe fresh air in control of the damper means controlling said fresh airinlet and said chamber, means for circulating air through said airconditioning chamber and a space to be conditioned, damper means incontrol ofsaid fresh air inlet, said return air inlet and said by-pass,means responsive to the temperature of the fresh airforcontrolling thedamper means in-control of the fresh air inlet and the return air inletto provide for admission of a maximum amount of fresh air and a minimumamount of return air when the temperature of the fresh air is at apredetermined value and to graduatingly decrease the amount of fresh airand to increase the amount of return air as the temperature of the freshair rises above or falls below said predetermined value, meansresponsive to the temperature of the return air also in control of thedamper means controlling said return air inlet and the damper meanscontrolling said by-pass to increase the amount of air admitted throughi said retum air inlet and to decrease the amount of air by-passedaround said cooling means as the temperature of the return air increasesabove a predetermined value, and means under the control of the-firstmentioned temperature re-* sponsive means for controlling the coolingeffect'of the cooling means.

5. In an air conditioning system, an air conditioning chamber having afresh air inlet, a return air inlet, cooling means within said chamber,means for conducting air from a space being conditioned to said returnair inlet, a bypass for conducting air from said conducting means aroundsaid cooling means to said conreturn air inlet, means responsive to thecondition of the return air also in control of the damper meanscontrolling said return air inlet and the damper means in control ofsaid bypass, means responsive to the dewpoint temperature of the airleaving the cooling means, and means under the control of thefirstmentioned condition responsive means and the dewpoint temperatureresponsive means for controlling the cooling effect of the coolingmeans.

6. In an air conditioning system, an air conditioning chamber having afresh air inlet, a return air inlet, cooling means within said chamber,means for controlling air from a space being conditioned to said returnair inlet, a by-pass for conducting air from said conducting meansaround said cooling means to said conditioning chamber, means forcirculating air through said air conditioning chamber and a space to beconditioned, damper means in control of said fresh air inlet, saidreturn air inlet and said by-pass, means responsive to the temperatureof the fresh air for controlling the damper means in control of thefresh air inlet and the return air inlet to provide for admission of amaximum amount of fresh air and a minimumamount of return air when thetemperature of the fresh air is at a predetermined value and togradually decrease the amount of fresh air and to increase the amount ofreturn air as the temperature of the fresh air rises above or fallsbelow said predetermined'value, means responsive to the temperature ofthe return air also in control of the damper means controlling saidreturn air inlet and the damper means controlling said by-pass toincrease the amount of air admitted through said return air inlet and todecrease the amount of air by-passed around said cooling means as thetemperature of the return air increases above a predetermined value,means responsive to the dewpoint temperature of the air leaving thecooling means, and means under the control of the first mentionedtemperature responsive means and the last mentioned temperatureresponsive means for controlling the cooling effect of the coolingmeans.

'7. In an air conditioning system, anair conditioning chamber havingafresh air inlet, a return air inlet, cooling means within saidchamber,means for conductingair from a space being conditioned to said returnair inlet, a by-pass for said return air inlet, the damper means incontrol of said by-pass, and the heating means in said by-pass, andmeans responsive to the dewpoint temperature of the air leaving saidcooling means also in control of said cooling means and the heatingmeans in said air conditioningchamber.

-8. In an air conditioning system, an air conditioning chamber having afresh air inlet, a return air inlet, cooling means within said chamber,

means for conducting air from a space being conditioned to said returnair inlet, a by=pass for conducting air from said conducting meansaround said cooling .means to said conditioning chamber, heating meansin said air conditioning chamber, heating means in said by-Dass, dampermeans in control of said fresh air inlet, said return air inlet and saidby-pass, means responsive 'to the temperature of .the fresh air incontrol of said cooling means and the damper means controlling the freshair inlet and the return air inlet, means responsive to the temperatureof the return air also in control of. the damper means controlling saidreturn air inlet, the damper means in control of said by-pass, and theheater in said by-pass, means responsive to the dewpoint temperature of.the air leaving said cooling means also in control of said coolingmeans and the heater in said air conditioning chamber, and meansresponsive to the temperature of air entering the space beingconditioned also in control of the heater in said by-pass.

9. In an air conditioning system, an air conditioning chamber having afresh air inlet, a return air inlet, cooling means within said chamber,means for conducting air from a space being conditioned to said returnair inlet, a by-pass for conducting air from said conducting meansaround said cooling means to said conditioning chamber, means forcirculating air through said air conditioning chamber and a space to beconditioned, damper means in control of said fresh air inlet, saidreturn air inlet and said by-pass, means responsive to outdoortemperature in control of the turn air also in control of the dampermeans controlling said return air inlet and said by-pass, and meansresponsive to the dewpoint temperature of the air leaving saidspray incontrol of said valve means.

11. In an air conditioning system, an airconditioning chamber having afresh air inlet, a return air inlet, cooling means within said chamber,means for conducting air from a space being conditioned for sprayingwater in said chamber,

means for recirculating said water through a cooling means, means forby-passing water around said cooling means, valve means in control ofsaid by-passing means, means for conducting air from the space beingconditioned to said return air inlet, a by-pass for conducting returnair to the air conditioning chamber around said water spraying means,damper means in control of said fresh air inlet, said return air inletand said by-pass, means responsive to outdoor temperature in control ofthe damper means controlling the fresh air inlet and the return airinlet, means responsive to return air temperature also in control of thedamper. means controlling said return air inlet and said bypass, andmeans responsive to the dewpoint temperature of the air leaving saidspray and under I the control 'of the first temperature responsivedamper means controlling the fresh air inlet to controlling the returnair inlet in an opposite sense from the damper means controllingtthefresh air inlet, whereby when the last named damper means are wide open,the other damper means are closed, a second temperature responsive meansalso in controlof the damper means controlling the return air inlet, andmeans for moving the damper means controlling said by-pass in anopposite sense from the movement of the damper means controlling thereturn air inlet when the last mentioned damper means are operated bysaid second temperature responsive means.

10. In an air conditioning system, an air conditioning chamber having afresh air inlet, a return air inlet, means for circulating air'throughsaid chamber and a space to be conditioned, means for spraying waterinsaid chamber, means for recirculating said water through a coolingmeans, means for by-passing water around said cooling means, valve meansin control of said by-passing means, means forconducting air from thespace being conditioned to said return air inlet, a bymeans in controlof said valve means.

12. In an air conditioning system for a space, a conditioning chamber,air conditioning means in said chamber for varying the condition of theair flowing through said chamber, means for causing air to fiow throughsaid chamber to said space, a fresh air inlet for said chamber fordelivering fresh air to the air conditioning means, a return air inletfor saidchamber fordelivering return air from;said space to said airconditioning means, a by-pass inlet for delivering air to said chamberdownstream of said conditioning means, fresh air damper means forcontrolling the fresh air inlet, return air damper means for controllingsaid return air inlet, a by-pass damper for controlling said by-pass,first control means for controlling the fresh air damper means andreturn air damper means in unison but in opposite manners for therebyvarying the proportions of fresh and return air supplied to said spacewhile maintaining the combined air flow substantially constant, andsecond control means for controlling said by-pass damper means and oneof said first mentioned damper means in unison but in opposite mannersfor changing the proportions of air passed through and bypassed aroundsaid air conditioning means without substantially varying theproportions of fresh and return airsupplied to said space.

13. In an air conditioning system for aspace, in combination, a firstsource of air for supply to a space, a second source of air, aconditioner connected for delivering conditioned air to a space, meansfor supplying air from said first and second sources to saidconditioner, first ,damper means for controlling the flow of air turnair supplied to said conditioner without subv stantially changing thetotal air flow, and and control means for controlling said by-passsecing the proportions of air from said first and second sources whichare supplied to said space.

14. In an air conditioning system for a space, a conditioningv chamber,air,conditioning means in said chamber for varying the condition of theair flowing through said chamber, means for causing air to flow throughsaid chamber to said space, a fresh air inlet for said chamber fordelivering fresh air to the air conditioning means, a return air inletfor said chamber for delivering return air from said space to said airconditioning means, a by-pass inlet for delivering return air to saidchamber downstream of said conditioning means, fresh air damper meansfor controlling the fresh air inlet, return air aas'mea for addingreturn air to the air downstream of said cooling means, fresh air dampermeans for controlling the flow of fresh air, return air damper means forcontrolling the flow of return air, by-pass damper means for controllingthe flow of air through said by-pass. first control means forcontrolling the fresh air damper means and return air damper means inunison but in opposite manners for varying the proportions of fresh andreturn air supplied to said space while maintaining the combined airflow substantially constant, and second control means for controllingsaid return air damper means and said by-pass damper means in unisondamper means for controlling said return air I inlet, a by-pass damperfor controlling said bypass, first control means for controlling thefresh air damper means and return air damper means in unison but inopposite manners for thereby varying the proportions of fresh and returnair supplied to said space while maintaining the combined air flowsubstantially constant, and second controlmeans for controlling saidby-pass damper means and said return air damper means in unison forthereby changing the proportions of return air passed through andby-passed around said conditioning means without substantially varyingthe proportions of fresh and return air supplied to said space.

15. In an air conditioning system for a space,

in combination, a conditioning chamber, cooling means in said chamber,means for causing air to flow through said chamber to said space, afresh air inlet for said chamber for delivering fresh air to saidcooling means, a return air inlet for said chambers for deliveringreturn air said space to said cooling means, a by-pass but in oppositemanners for varying the proportions of return air passed through andby-passed around said cooling means without substantially varying theproportions of fresh and return air supplied to said space.

18. In an air conditioning system for a space, in combination, aconditioning chamber, an air conditioning device insaid chamber, a freshair inlet for said chamber for delivering fresh air to said conditioningdevice. a return air inlet for said chamber for delivering return airfrom said space to said conditioning device, a by-pass for adding onlyreturnv air' to the air downstream of said conditioning device, a returnair damper for controlling the flow of'return air, a by-pass damper forcontrolling the flow of air through said by-pass, controlomeansresponsive to a condition which is a measure of the demand forconditioning by said conditioning device for controlling said return airdamper and said by-pass damper in unison but in opposite'manners forthereby varying the flow of air through said conditioning device, afresh air damper for controlling the flow of fresh air, and controlmeans for controlling said fresh air damper and one of said other airdampers in a manner to vary the proportions of fresh and return airsupplied to said space.

GORDON H. GILDERSLEEVE. ERNEST GRABER.

CERTIFICATE OF CORRECTION. I, Patent No. 2,257JL62. I September 50, 1911.

GORDON H. GILDERSLEEVE, ET At.

It is hereby certified that error appears in the printed specificationofthe above numbered patent requiring correction as follows: Page 5,second column, line 75, strike out "65 to 75, Thns at 65 the arm l25will be at" and insert the same after "example", line 71; page 9, secondcolumn, line 21, claim 6, for "controlling" read -conducting--; line 55,

same claim, for "gradually" read -grad1 1atingly--; and that thesaid'Letters Patent should be read with this correction therein that thesame may conform to the record of the case in the Patent Office.

Signed and sealed this 114th day of April, A. D. 191E.

Henry Van Arsdale, (Seal) 1 Acting Commissioner of Patents.

